<!DOCTYPE html>
<html lang="en" dir="ltr" class="client-nojs">
<head>
<title>Mathematical constants - cppreference.com</title>
<meta charset="UTF-8">
<meta name="generator" content="MediaWiki 1.21.2">
<link rel="shortcut icon" href="../../../common/favicon.ico">
<link rel="stylesheet" href="../../../common/ext.css">
<meta name="ResourceLoaderDynamicStyles" content="">
<link rel="stylesheet" href="../../../common/site_modules.css">
<style>a:lang(ar),a:lang(ckb),a:lang(fa),a:lang(kk-arab),a:lang(mzn),a:lang(ps),a:lang(ur){text-decoration:none}#toc{display:none}.editsection{display:none}
/* cache key: mwiki1-mwiki_en_:resourceloader:filter:minify-css:7:472787eddcf4605d11de8c7ef047234f */</style>

<script src="../../../common/startup_scripts.js"></script>
<script>if(window.mw){
mw.config.set({"wgCanonicalNamespace":"","wgCanonicalSpecialPageName":false,"wgNamespaceNumber":0,"wgPageName":"cpp/numeric/constants","wgTitle":"cpp/numeric/constants","wgCurRevisionId":141025,"wgArticleId":18592,"wgIsArticle":true,"wgAction":"view","wgUserName":null,"wgUserGroups":["*"],"wgCategories":[],"wgBreakFrames":false,"wgPageContentLanguage":"en","wgSeparatorTransformTable":["",""],"wgDigitTransformTable":["",""],"wgDefaultDateFormat":"dmy","wgMonthNames":["","January","February","March","April","May","June","July","August","September","October","November","December"],"wgMonthNamesShort":["","Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"],"wgRelevantPageName":"cpp/numeric/constants","wgRestrictionEdit":[],"wgRestrictionMove":[]});
}</script><script>if(window.mw){
mw.loader.implement("user.options",function(){mw.user.options.set({"ccmeonemails":0,"cols":80,"date":"default","diffonly":0,"disablemail":0,"disablesuggest":0,"editfont":"default","editondblclick":0,"editsection":0,"editsectiononrightclick":0,"enotifminoredits":0,"enotifrevealaddr":0,"enotifusertalkpages":1,"enotifwatchlistpages":0,"extendwatchlist":0,"externaldiff":0,"externaleditor":0,"fancysig":0,"forceeditsummary":0,"gender":"unknown","hideminor":0,"hidepatrolled":0,"imagesize":2,"justify":0,"math":1,"minordefault":0,"newpageshidepatrolled":0,"nocache":0,"noconvertlink":0,"norollbackdiff":0,"numberheadings":0,"previewonfirst":0,"previewontop":1,"quickbar":5,"rcdays":7,"rclimit":50,"rememberpassword":0,"rows":25,"searchlimit":20,"showhiddencats":0,"showjumplinks":1,"shownumberswatching":1,"showtoc":0,"showtoolbar":1,"skin":"cppreference2","stubthreshold":0,"thumbsize":2,"underline":2,"uselivepreview":0,"usenewrc":0,"watchcreations":0,"watchdefault":0,"watchdeletion":0,
"watchlistdays":3,"watchlisthideanons":0,"watchlisthidebots":0,"watchlisthideliu":0,"watchlisthideminor":0,"watchlisthideown":0,"watchlisthidepatrolled":0,"watchmoves":0,"wllimit":250,"variant":"en","language":"en","searchNs0":true,"searchNs1":false,"searchNs2":false,"searchNs3":false,"searchNs4":false,"searchNs5":false,"searchNs6":false,"searchNs7":false,"searchNs8":false,"searchNs9":false,"searchNs10":false,"searchNs11":false,"searchNs12":false,"searchNs13":false,"searchNs14":false,"searchNs15":false,"gadget-ColiruCompiler":1,"gadget-MathJax":1});;},{},{});mw.loader.implement("user.tokens",function(){mw.user.tokens.set({"editToken":"+\\","patrolToken":false,"watchToken":false});;},{},{});
/* cache key: mwiki1-mwiki_en_:resourceloader:filter:minify-js:7:9f05c6caceb9bb1a482b6cebd4c5a330 */
}</script>
<script>if(window.mw){
mw.loader.load(["mediawiki.page.startup","mediawiki.legacy.wikibits","mediawiki.legacy.ajax"]);
}</script>
<style type="text/css">/*<![CDATA[*/
.source-cpp {line-height: normal;}
.source-cpp li, .source-cpp pre {
	line-height: normal; border: 0px none white;
}
/**
 * GeSHi Dynamically Generated Stylesheet
 * --------------------------------------
 * Dynamically generated stylesheet for cpp
 * CSS class: source-cpp, CSS id: 
 * GeSHi (C) 2004 - 2007 Nigel McNie, 2007 - 2008 Benny Baumann
 * (http://qbnz.com/highlighter/ and http://geshi.org/)
 * --------------------------------------
 */
.cpp.source-cpp .de1, .cpp.source-cpp .de2 {font: normal normal 1em/1.2em monospace; margin:0; padding:0; background:none; vertical-align:top;}
.cpp.source-cpp  {font-family:monospace;}
.cpp.source-cpp .imp {font-weight: bold; color: red;}
.cpp.source-cpp li, .cpp.source-cpp .li1 {font-weight: normal; vertical-align:top;}
.cpp.source-cpp .ln {width:1px;text-align:right;margin:0;padding:0 2px;vertical-align:top;}
.cpp.source-cpp .li2 {font-weight: bold; vertical-align:top;}
.cpp.source-cpp .kw1 {color: #0000dd;}
.cpp.source-cpp .kw2 {color: #0000ff;}
.cpp.source-cpp .kw3 {color: #0000dd;}
.cpp.source-cpp .kw4 {color: #0000ff;}
.cpp.source-cpp .co1 {color: #909090;}
.cpp.source-cpp .co2 {color: #339900;}
.cpp.source-cpp .coMULTI {color: #ff0000; font-style: italic;}
.cpp.source-cpp .es0 {color: #008000; font-weight: bold;}
.cpp.source-cpp .es1 {color: #008000; font-weight: bold;}
.cpp.source-cpp .es2 {color: #008000; font-weight: bold;}
.cpp.source-cpp .es3 {color: #008000; font-weight: bold;}
.cpp.source-cpp .es4 {color: #008000; font-weight: bold;}
.cpp.source-cpp .es5 {color: #008000; font-weight: bold;}
.cpp.source-cpp .br0 {color: #008000;}
.cpp.source-cpp .sy0 {color: #008000;}
.cpp.source-cpp .sy1 {color: #000080;}
.cpp.source-cpp .sy2 {color: #000040;}
.cpp.source-cpp .sy3 {color: #000040;}
.cpp.source-cpp .sy4 {color: #008080;}
.cpp.source-cpp .st0 {color: #008000;}
.cpp.source-cpp .nu0 {color: #000080;}
.cpp.source-cpp .nu6 {color: #000080;}
.cpp.source-cpp .nu8 {color: #000080;}
.cpp.source-cpp .nu12 {color: #000080;}
.cpp.source-cpp .nu16 {color:#000080;}
.cpp.source-cpp .nu17 {color:#000080;}
.cpp.source-cpp .nu18 {color:#000080;}
.cpp.source-cpp .nu19 {color:#000080;}
.cpp.source-cpp .ln-xtra, .cpp.source-cpp li.ln-xtra, .cpp.source-cpp div.ln-xtra {background-color: #ffc;}
.cpp.source-cpp span.xtra { display:block; }

/*]]>*/
</style><style type="text/css">/*<![CDATA[*/
.source-text {line-height: normal;}
.source-text li, .source-text pre {
	line-height: normal; border: 0px none white;
}
/**
 * GeSHi Dynamically Generated Stylesheet
 * --------------------------------------
 * Dynamically generated stylesheet for text
 * CSS class: source-text, CSS id: 
 * GeSHi (C) 2004 - 2007 Nigel McNie, 2007 - 2008 Benny Baumann
 * (http://qbnz.com/highlighter/ and http://geshi.org/)
 * --------------------------------------
 */
.text.source-text .de1, .text.source-text .de2 {font: normal normal 1em/1.2em monospace; margin:0; padding:0; background:none; vertical-align:top;}
.text.source-text  {font-family:monospace;}
.text.source-text .imp {font-weight: bold; color: red;}
.text.source-text li, .text.source-text .li1 {font-weight: normal; vertical-align:top;}
.text.source-text .ln {width:1px;text-align:right;margin:0;padding:0 2px;vertical-align:top;}
.text.source-text .li2 {font-weight: bold; vertical-align:top;}
.text.source-text .ln-xtra, .text.source-text li.ln-xtra, .text.source-text div.ln-xtra {background-color: #ffc;}
.text.source-text span.xtra { display:block; }

/*]]>*/
</style><!--[if lt IE 7]><style type="text/css">body{behavior:url("/mwiki/skins/cppreference2/csshover.min.htc")}</style><![endif]--></head>
<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_numeric_constants skin-cppreference2 action-view cpp-navbar">
        <!-- header -->
        <!-- /header -->
        <!-- content -->
<div id="cpp-content-base">
            <div id="content">
                <a id="top"></a>
                <div id="mw-js-message" style="display:none;"></div>
                                <!-- firstHeading -->
<h1 id="firstHeading" class="firstHeading">Mathematical constants</h1>
                <!-- /firstHeading -->
                <!-- bodyContent -->
                <div id="bodyContent">
                                        <!-- tagline -->
                    <div id="siteSub">From cppreference.com</div>
                    <!-- /tagline -->
                                        <!-- subtitle -->
                    <div id="contentSub"><span class="subpages">&lt; <a href="../../cpp.html" title="cpp">cpp</a>‎ | <a href="../numeric.html" title="cpp/numeric">numeric</a></span></div>
                    <!-- /subtitle -->
                                                            <!-- bodycontent -->
                    <div id="mw-content-text" lang="en" dir="ltr" class="mw-content-ltr"><div class="t-navbar" style=""><div class="t-navbar-sep"> </div><div class="t-navbar-head"><a href="../../cpp.html" title="cpp"> C++</a><div class="t-navbar-menu"><div><div><table class="t-nv-begin" cellpadding="0" style="line-height:1.1em;">
<tr class="t-nv"><td colspan="5"> <a href="../compiler_support.html" title="cpp/compiler support"> Compiler support</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../freestanding.html" title="cpp/freestanding"> Freestanding and hosted</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../language.html" title="cpp/language"> Language</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../header.html" title="cpp/header"> Standard library headers</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../named_req.html" title="cpp/named req"> Named requirements </a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../feature_test.html" title="cpp/feature test"> Feature test macros </a> <span class="t-mark-rev t-since-cxx20">(C++20)</span> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../utility.html#Language_support" title="cpp/utility"> Language support library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../concepts.html" title="cpp/concepts"> Concepts library</a> <span class="t-mark-rev t-since-cxx20">(C++20)</span> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../meta.html" title="cpp/meta"> Metaprogramming library</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../error.html" title="cpp/error"> Diagnostics library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../utility.html" title="cpp/utility"> General utilities library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../string.html" title="cpp/string"> Strings library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../container.html" title="cpp/container"> Containers library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../iterator.html" title="cpp/iterator"> Iterators library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../ranges.html" title="cpp/ranges"> Ranges library</a> <span class="t-mark-rev t-since-cxx20">(C++20)</span> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../algorithm.html" title="cpp/algorithm"> Algorithms library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../numeric.html" title="cpp/numeric"> Numerics library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../locale.html" title="cpp/locale"> Localizations library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../io.html" title="cpp/io"> Input/output library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../filesystem.html" title="cpp/filesystem"> Filesystem library</a> <span class="t-mark-rev t-since-cxx17">(C++17)</span> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../regex.html" title="cpp/regex"> Regular expressions library</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../thread.html" title="cpp/thread"> Concurrency support library</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../experimental.html" title="cpp/experimental"> Technical specifications</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../symbol_index.html" title="cpp/symbol index"> Symbols index</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../links/libs.html" title="cpp/links/libs"> External libraries</a> </td></tr>
</table></div><div></div></div></div></div><div class="t-navbar-sep"> </div><div class="t-navbar-head"><a href="../numeric.html" title="cpp/numeric"> Numerics library</a><div class="t-navbar-menu"><div><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="math.html" title="cpp/numeric/math">Common mathematical functions</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="special_functions.html" title="cpp/numeric/special functions">Mathematical special functions</a> <span class="t-mark-rev t-since-cxx17">(C++17)</span> </td></tr>
<tr class="t-nv"><td colspan="5"> <strong class="selflink">Mathematical constants</strong> <span class="t-mark-rev t-since-cxx20">(C++20)</span> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="fenv.html" title="cpp/numeric/fenv">Floating-point environment</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="complex.html" title="cpp/numeric/complex">Complex numbers</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="valarray.html" title="cpp/numeric/valarray">Numeric arrays</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="random.html" title="cpp/numeric/random">Pseudo-random number generation</a> </td></tr>
<tr class="t-nv-h2"><td colspan="5"> <a href="../numeric.html#Factor_operations" title="cpp/numeric">Factor operations</a> </td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="gcd.html" title="cpp/numeric/gcd"><span class="t-lines"><span>gcd</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="lcm.html" title="cpp/numeric/lcm"><span class="t-lines"><span>lcm</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span></span></div></div></td></tr>
<tr class="t-nv-h2"><td colspan="5"> <a href="../numeric.html#Interpolation_operations" title="cpp/numeric">Interpolations</a> </td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="midpoint.html" title="cpp/numeric/midpoint"><span class="t-lines"><span>midpoint</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="lerp.html" title="cpp/numeric/lerp"><span class="t-lines"><span>lerp</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div></td></tr>
<tr class="t-nv-h2"><td colspan="5"> <a href="../numeric.html#Numeric_operations" title="cpp/numeric">Generic numeric operations</a> </td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="../algorithm/iota.html" title="cpp/algorithm/iota"><span class="t-lines"><span>iota</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="../algorithm/ranges/iota.html" title="cpp/algorithm/ranges/iota"><span class="t-lines"><span>ranges::iota</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx23">(C++23)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="../algorithm/accumulate.html" title="cpp/algorithm/accumulate"><span class="t-lines"><span>accumulate</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="../algorithm/inner_product.html" title="cpp/algorithm/inner product"><span class="t-lines"><span>inner_product</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="../algorithm/adjacent_difference.html" title="cpp/algorithm/adjacent difference"><span class="t-lines"><span>adjacent_difference</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="../algorithm/partial_sum.html" title="cpp/algorithm/partial sum"><span class="t-lines"><span>partial_sum</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="../algorithm/reduce.html" title="cpp/algorithm/reduce"><span class="t-lines"><span>reduce</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="../algorithm/transform_reduce.html" title="cpp/algorithm/transform reduce"><span class="t-lines"><span>transform_reduce</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="../algorithm/inclusive_scan.html" title="cpp/algorithm/inclusive scan"><span class="t-lines"><span>inclusive_scan</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="../algorithm/exclusive_scan.html" title="cpp/algorithm/exclusive scan"><span class="t-lines"><span>exclusive_scan</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="../algorithm/transform_inclusive_scan.html" title="cpp/algorithm/transform inclusive scan"><span class="t-lines"><span>transform_inclusive_scan</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="../algorithm/transform_exclusive_scan.html" title="cpp/algorithm/transform exclusive scan"><span class="t-lines"><span>transform_exclusive_scan</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span></span></div></div></td></tr>
<tr class="t-nv-h2"><td colspan="5"> <a href="../numeric.html#Bit_manipulation_.28since_C.2B.2B20.29" title="cpp/numeric">Bit operations</a></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="bit_cast.html" title="cpp/numeric/bit cast"><span class="t-lines"><span>bit_cast</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="byteswap.html" title="cpp/numeric/byteswap"><span class="t-lines"><span>byteswap</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx23">(C++23)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="has_single_bit.html" title="cpp/numeric/has single bit"><span class="t-lines"><span>has_single_bit</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="bit_ceil.html" title="cpp/numeric/bit ceil"><span class="t-lines"><span>bit_ceil</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="bit_floor.html" title="cpp/numeric/bit floor"><span class="t-lines"><span>bit_floor</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="bit_width.html" title="cpp/numeric/bit width"><span class="t-lines"><span>bit_width</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="rotl.html" title="cpp/numeric/rotl"><span class="t-lines"><span>rotl</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="rotr.html" title="cpp/numeric/rotr"><span class="t-lines"><span>rotr</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="countl_zero.html" title="cpp/numeric/countl zero"><span class="t-lines"><span>countl_zero</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="countl_one.html" title="cpp/numeric/countl one"><span class="t-lines"><span>countl_one</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="countr_zero.html" title="cpp/numeric/countr zero"><span class="t-lines"><span>countr_zero</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="countr_one.html" title="cpp/numeric/countr one"><span class="t-lines"><span>countr_one</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="popcount.html" title="cpp/numeric/popcount"><span class="t-lines"><span>popcount</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="../types/endian.html" title="cpp/types/endian"><span class="t-lines"><span>endian</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div></td></tr>
</table></div><div></div></div></div></div><div class="t-navbar-sep"> </div><div class="t-navbar-head"><strong class="selflink"> Mathematical constants</strong></div><div class="t-navbar-sep"> </div></div>
<h3><span class="mw-headline" id="Constants_.28since_C.2B.2B20.29"> Constants <span class="t-mark-rev t-since-cxx20">(since C++20)</span> </span></h3>
<table class="t-dsc-begin">

<tr class="t-dsc-header">
<td colspan="2"> <div>Defined in header <code><a href="../header/numbers.html" title="cpp/header/numbers">&lt;numbers&gt;</a></code> </div>
</td></tr>

<tr class="t-dsc-header">
<td colspan="2"> <div>Defined in  namespace <code>std::numbers</code> </div>
</td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span>e_v</span></span></div></div>
</td>
<td>   <a href="https://en.wikipedia.org/wiki/E_(mathematical_constant)" class="extiw" title="enwiki:E (mathematical constant)">the mathematical constant <span class="mjax" style="display:none">\(\small e\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;">e</span></a>  <br> <span class="t-mark">(variable template)</span>
</td></tr>


<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span>log2e_v</span></span></div></div>
</td>
<td>   <span class="mjax" style="display:none">\(\log_{2}e\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;">log<span class="t-su t-su-b"><br>2</span>e</span> <br> <span class="t-mark">(variable template)</span>
</td></tr>


<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span>log10e_v</span></span></div></div>
</td>
<td>   <span class="mjax" style="display:none">\(\log_{10}e\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;">log<span class="t-su t-su-b"><br>10</span>e</span> <br> <span class="t-mark">(variable template)</span>
</td></tr>


<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span>pi_v</span></span></div></div>
</td>
<td>   <a href="https://en.wikipedia.org/wiki/Pi_(mathematical_constant)" class="extiw" title="enwiki:Pi (mathematical constant)">the mathematical constant <span class="mjax" style="display:none">\(\pi\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;">π</span></a>  <br> <span class="t-mark">(variable template)</span>
</td></tr>


<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span>inv_pi_v</span></span></div></div>
</td>
<td>   <span class="mjax" style="display:none">\(\frac1\pi\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;"><span class="t-mfrac"><table><tr><td>1</td></tr><tr><td>π</td></tr></table></span></span>  <br> <span class="t-mark">(variable template)</span>
</td></tr>


<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span>inv_sqrtpi_v</span></span></div></div>
</td>
<td>   <span class="mjax" style="display:none">\(\frac1{\sqrt\pi}\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;"><span class="t-mfrac"><table><tr><td>1</td></tr><tr><td><span class="t-mrad"><span>√</span><span>π</span></span> </td></tr></table></span></span>  <br> <span class="t-mark">(variable template)</span>
</td></tr>


<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span>ln2_v</span></span></div></div>
</td>
<td>   <span class="mjax" style="display:none">\(\ln{2}\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;">ln 2</span> <br> <span class="t-mark">(variable template)</span>
</td></tr>


<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span>ln10_v</span></span></div></div>
</td>
<td>   <span class="mjax" style="display:none">\(\ln{10}\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;">ln 10</span> <br> <span class="t-mark">(variable template)</span>
</td></tr>


<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span>sqrt2_v</span></span></div></div>
</td>
<td>  <span class="mjax" style="display:none">\(\sqrt2\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;"><span class="t-mrad"><span>√</span><span>2</span></span></span> <br> <span class="t-mark">(variable template)</span>
</td></tr>


<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span>sqrt3_v</span></span></div></div>
</td>
<td>  <span class="mjax" style="display:none">\(\sqrt3\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;"><span class="t-mrad"><span>√</span><span>3</span></span></span> <br> <span class="t-mark">(variable template)</span>
</td></tr>


<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span>inv_sqrt3_v</span></span></div></div>
</td>
<td>   <span class="mjax" style="display:none">\(\frac1{\sqrt3}\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;"><span class="t-mfrac"><table><tr><td>1</td></tr><tr><td><span class="t-mrad"><span>√</span><span>3</span></span> </td></tr></table></span></span>  <br> <span class="t-mark">(variable template)</span>
</td></tr>


<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span>egamma_v</span></span></div></div>
</td>
<td>   <a href="https://en.wikipedia.org/wiki/Euler%E2%80%93Mascheroni_constant" class="extiw" title="enwiki:Euler–Mascheroni constant">the Euler–Mascheroni constant</a>  <br> <span class="t-mark">(variable template)</span>
</td></tr>


<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span>phi_v</span></span></div></div>
</td>
<td>   <a href="https://en.wikipedia.org/wiki/Golden_ratio" class="extiw" title="enwiki:Golden ratio">the golden ratio Φ constant</a> (<span class="mjax" style="display:none">\(\frac{1+\sqrt5}2\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;"><span class="t-mfrac"><table><tr><td>1 + <span class="t-mrad"><span>√</span><span>5</span></span></td></tr><tr><td>2</td></tr></table></span></span>)  <br> <span class="t-mark">(variable template)</span>
</td></tr>


<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span><span class="t-dsc-small">inline constexpr double</span> e</span></span></div></div>
</td>
<td>   <span class="t-c"><span class="mw-geshi cpp source-cpp">e_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span></span></span>  <br> <span class="t-mark">(constant)</span>
</td></tr>


<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span><span class="t-dsc-small">inline constexpr double</span> log2e</span></span></div></div>
</td>
<td>   <span class="t-c"><span class="mw-geshi cpp source-cpp">log2e_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span></span></span>  <br> <span class="t-mark">(constant)</span>
</td></tr>


<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span><span class="t-dsc-small">inline constexpr double</span> log10e</span></span></div></div>
</td>
<td>   <span class="t-c"><span class="mw-geshi cpp source-cpp">log10e_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span></span></span>  <br> <span class="t-mark">(constant)</span>
</td></tr>


<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span><span class="t-dsc-small">inline constexpr double</span> pi</span></span></div></div>
</td>
<td>   <span class="t-c"><span class="mw-geshi cpp source-cpp">pi_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span></span></span>  <br> <span class="t-mark">(constant)</span>
</td></tr>


<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span><span class="t-dsc-small">inline constexpr double</span> inv_pi</span></span></div></div>
</td>
<td>   <span class="t-c"><span class="mw-geshi cpp source-cpp">inv_pi_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span></span></span>  <br> <span class="t-mark">(constant)</span>
</td></tr>


<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span><span class="t-dsc-small">inline constexpr double</span> inv_sqrtpi</span></span></div></div>
</td>
<td>   <span class="t-c"><span class="mw-geshi cpp source-cpp">inv_sqrtpi_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span></span></span>  <br> <span class="t-mark">(constant)</span>
</td></tr>


<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span><span class="t-dsc-small">inline constexpr double</span> ln2</span></span></div></div>
</td>
<td>   <span class="t-c"><span class="mw-geshi cpp source-cpp">ln2_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span></span></span>  <br> <span class="t-mark">(constant)</span>
</td></tr>


<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span><span class="t-dsc-small">inline constexpr double</span> ln10</span></span></div></div>
</td>
<td>   <span class="t-c"><span class="mw-geshi cpp source-cpp">ln10_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span></span></span>  <br> <span class="t-mark">(constant)</span>
</td></tr>


<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span><span class="t-dsc-small">inline constexpr double</span> sqrt2</span></span></div></div>
</td>
<td>   <span class="t-c"><span class="mw-geshi cpp source-cpp">sqrt2_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span></span></span>  <br> <span class="t-mark">(constant)</span>
</td></tr>


<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span><span class="t-dsc-small">inline constexpr double</span> sqrt3</span></span></div></div>
</td>
<td>   <span class="t-c"><span class="mw-geshi cpp source-cpp">sqrt3_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span></span></span>  <br> <span class="t-mark">(constant)</span>
</td></tr>


<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span><span class="t-dsc-small">inline constexpr double</span> inv_sqrt3</span></span></div></div>
</td>
<td>   <span class="t-c"><span class="mw-geshi cpp source-cpp">inv_sqrt3_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span></span></span>  <br> <span class="t-mark">(constant)</span>
</td></tr>


<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span><span class="t-dsc-small">inline constexpr double</span> egamma</span></span></div></div>
</td>
<td>   <span class="t-c"><span class="mw-geshi cpp source-cpp">egamma_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span></span></span>  <br> <span class="t-mark">(constant)</span>
</td></tr>


<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><span class="t-lines"><span><span class="t-dsc-small">inline constexpr double</span> phi</span></span></div></div>
</td>
<td>   <span class="t-c"><span class="mw-geshi cpp source-cpp">phi_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span></span></span>  <br> <span class="t-mark">(constant)</span>
</td></tr>

</table>
<h3><span class="mw-headline" id="Notes">Notes</span></h3>
<p>A program that instantiates a primary template of a mathematical constant variable template is ill-formed.
</p><p>The standard library specializes mathematical constant variable templates for all floating-point types (i.e. <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">float</span></span></span>, <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">double</span></span></span> and <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">long</span> <span class="kw4">double</span></span></span>).
</p><p>A program may partially or explicitly specialize a mathematical constant variable template provided that the specialization depends on a program-defined type.
</p>
<table class="wikitable">
<tr>
<td> <a href="../feature_test.html#Library_features" title="cpp/feature test">Feature-test</a> macro:
</td>
<td> <a href="../utility/feature_test.html" title="cpp/utility/feature test"><tt>__cpp_lib_math_constants</tt></a>
</td></tr></table>
<h3><span class="mw-headline" id="Example">Example</span></h3>
<div class="t-example"><div class="t-example-live-link"><div class="coliru-btn coliru-btn-run-init">Run this code</div></div>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="co2">#include &lt;cmath&gt;</span>
<span class="co2">#include &lt;iomanip&gt;</span>
<span class="co2">#include &lt;iostream&gt;</span>
<span class="co2">#include &lt;limits&gt;</span>
<span class="co2">#include &lt;numbers&gt;</span>
<span class="co2">#include &lt;string_view&gt;</span>
<span class="co2">#include &lt;functional&gt;</span>
 
<span class="kw1">using</span> std<span class="sy4">::</span><span class="me2">placeholders</span><span class="sy4">::</span>_2<span class="sy4">;</span>
<span class="kw1">template</span> <span class="sy1">&lt;</span><span class="kw1">class</span> T<span class="sy1">&gt;</span>
<span class="kw4">constexpr</span> <span class="kw4">auto</span> operator<span class="sy3">^</span><span class="br0">(</span>T base, decltype<span class="br0">(</span>_2<span class="br0">)</span><span class="br0">)</span> <span class="br0">{</span> <span class="kw1">return</span> base <span class="sy2">*</span> base<span class="sy4">;</span> <span class="br0">}</span>
 
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
    <span class="kw1">using</span> <span class="kw1">namespace</span> std<span class="sy4">::</span><span class="me2">numbers</span><span class="sy4">;</span>
 
    <a href="../io/cout.html"><span class="kw1762">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">"The answer is "</span> <span class="sy1">&lt;&lt;</span>
        <span class="br0">(</span><span class="br0">(</span><span class="br0">(</span><a href="math/sin.html"><span class="kw1336">std::<span class="me2">sin</span></span></a><span class="br0">(</span>e<span class="br0">)</span><span class="sy3">^</span>_2<span class="br0">)</span> <span class="sy2">+</span> <span class="br0">(</span><a href="math/cos.html"><span class="kw1337">std::<span class="me2">cos</span></span></a><span class="br0">(</span>e<span class="br0">)</span><span class="sy3">^</span>_2<span class="br0">)</span><span class="br0">)</span> <span class="sy2">+</span> 
        <a href="math/pow.html"><span class="kw1335">std::<span class="me2">pow</span></span></a><span class="br0">(</span>e, ln2<span class="br0">)</span> <span class="sy2">+</span> <a href="math/sqrt.html"><span class="kw1332">std::<span class="me2">sqrt</span></span></a><span class="br0">(</span>pi<span class="br0">)</span> <span class="sy2">*</span> inv_sqrtpi <span class="sy2">+</span>
        <span class="br0">(</span><span class="br0">(</span><a href="math/cosh.html"><span class="kw1344">std::<span class="me2">cosh</span></span></a><span class="br0">(</span>pi<span class="br0">)</span><span class="sy3">^</span>_2<span class="br0">)</span> <span class="sy2">-</span> <span class="br0">(</span><a href="math/sinh.html"><span class="kw1343">std::<span class="me2">sinh</span></span></a><span class="br0">(</span>pi<span class="br0">)</span><span class="sy3">^</span>_2<span class="br0">)</span><span class="br0">)</span> <span class="sy2">+</span>
        sqrt3 <span class="sy2">*</span> inv_sqrt3 <span class="sy2">*</span> log2e <span class="sy2">*</span> ln2 <span class="sy2">*</span> log10e <span class="sy2">*</span> ln10 <span class="sy2">*</span>
        pi <span class="sy2">*</span> inv_pi <span class="sy2">+</span> <span class="br0">(</span>phi <span class="sy2">*</span> phi <span class="sy2">-</span> phi<span class="br0">)</span><span class="br0">)</span> <span class="sy2">*</span>
        <span class="br0">(</span><span class="br0">(</span>sqrt2 <span class="sy2">*</span> sqrt3<span class="br0">)</span><span class="sy3">^</span>_2<span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
 
    <span class="kw4">auto</span> egamma_aprox <span class="sy1">=</span> <span class="br0">[</span><span class="br0">]</span> <span class="br0">(</span><span class="kw4">unsigned</span> <span class="kw4">const</span> iterations<span class="br0">)</span> <span class="br0">{</span>
        <span class="kw4">long</span> <span class="kw4">double</span> s<span class="br0">{</span><span class="br0">}</span>, m<span class="br0">{</span><span class="nu16">2.0</span><span class="br0">}</span><span class="sy4">;</span>
        <span class="kw1">for</span> <span class="br0">(</span><span class="kw4">unsigned</span> c<span class="br0">{</span><span class="nu0">2</span><span class="br0">}</span><span class="sy4">;</span> c <span class="sy3">!</span><span class="sy1">=</span> iterations<span class="sy4">;</span> <span class="sy2">++</span>c, <span class="sy2">++</span>m<span class="br0">)</span> <span class="br0">{</span>
            <span class="kw4">const</span> <span class="kw4">long</span> <span class="kw4">double</span> t<span class="br0">{</span> <a href="special_functions/riemann_zeta.html"><span class="kw1441">std::<span class="me2">riemann_zeta</span></span></a><span class="br0">(</span>m<span class="br0">)</span> <span class="sy2">/</span> m <span class="br0">}</span><span class="sy4">;</span>
            <span class="br0">(</span>c <span class="sy3">&amp;</span> <span class="nu0">1</span><span class="br0">)</span> <span class="sy1">==</span> <span class="nu0">0</span> <span class="sy4">?</span> s <span class="sy2">+</span><span class="sy1">=</span> t <span class="sy4">:</span> s <span class="sy2">-</span><span class="sy1">=</span> t<span class="sy4">;</span>
        <span class="br0">}</span>
        <span class="kw1">return</span> s<span class="sy4">;</span>
    <span class="br0">}</span><span class="sy4">;</span>
 
    <span class="kw4">constexpr</span> <a href="../string/basic_string_view.html"><span class="kw1251">std::<span class="me2">string_view</span></span></a> γ <span class="br0">{</span><span class="st0">"0.577215664901532860606512090082402"</span><span class="br0">}</span><span class="sy4">;</span>
 
    <a href="../io/cout.html"><span class="kw1762">std::<span class="me2">cout</span></span></a> 
        <span class="sy1">&lt;&lt;</span> <span class="st0">"γ as 10⁶ sums of ±ζ(m)/m   = "</span>
        <span class="sy1">&lt;&lt;</span> egamma_aprox<span class="br0">(</span><span class="nu0">1</span><span class="st0">'000'</span><span class="nu8">000</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">'<span class="es1">\n</span>'</span>
        <span class="sy1">&lt;&lt;</span> <span class="st0">"γ as egamma_v&lt;float&gt;       = "</span>
        <span class="sy1">&lt;&lt;</span> <a href="../io/manip/setprecision.html"><span class="kw1800">std::<span class="me2">setprecision</span></span></a><span class="br0">(</span><a href="../types/numeric_limits.html"><span class="kw350">std::<span class="me2">numeric_limits</span></span></a><span class="sy1">&lt;</span><span class="kw4">float</span><span class="sy1">&gt;</span><span class="sy4">::</span><span class="me2">digits10</span> <span class="sy2">+</span> <span class="nu0">1</span><span class="br0">)</span>
        <span class="sy1">&lt;&lt;</span> egamma_v<span class="sy1">&lt;</span><span class="kw4">float</span><span class="sy1">&gt;</span> <span class="sy1">&lt;&lt;</span> <span class="st0">'<span class="es1">\n</span>'</span>
        <span class="sy1">&lt;&lt;</span> <span class="st0">"γ as egamma_v&lt;double&gt;      = "</span>
        <span class="sy1">&lt;&lt;</span> <a href="../io/manip/setprecision.html"><span class="kw1800">std::<span class="me2">setprecision</span></span></a><span class="br0">(</span><a href="../types/numeric_limits.html"><span class="kw350">std::<span class="me2">numeric_limits</span></span></a><span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span><span class="sy4">::</span><span class="me2">digits10</span> <span class="sy2">+</span> <span class="nu0">1</span><span class="br0">)</span>
        <span class="sy1">&lt;&lt;</span> egamma_v<span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span> <span class="sy1">&lt;&lt;</span> <span class="st0">'<span class="es1">\n</span>'</span>
        <span class="sy1">&lt;&lt;</span> <span class="st0">"γ as egamma_v&lt;long double&gt; = "</span>
        <span class="sy1">&lt;&lt;</span> <a href="../io/manip/setprecision.html"><span class="kw1800">std::<span class="me2">setprecision</span></span></a><span class="br0">(</span><a href="../types/numeric_limits.html"><span class="kw350">std::<span class="me2">numeric_limits</span></span></a><span class="sy1">&lt;</span><span class="kw4">long</span> <span class="kw4">double</span><span class="sy1">&gt;</span><span class="sy4">::</span><span class="me2">digits10</span> <span class="sy2">+</span> <span class="nu0">1</span><span class="br0">)</span>
        <span class="sy1">&lt;&lt;</span> egamma_v<span class="sy1">&lt;</span><span class="kw4">long</span> <span class="kw4">double</span><span class="sy1">&gt;</span> <span class="sy1">&lt;&lt;</span> <span class="st0">'<span class="es1">\n</span>'</span>
        <span class="sy1">&lt;&lt;</span> <span class="st0">"γ with "</span> <span class="sy1">&lt;&lt;</span> γ.<span class="me1">length</span><span class="br0">(</span><span class="br0">)</span> <span class="sy2">-</span> <span class="nu0">1</span> <span class="sy1">&lt;&lt;</span> <span class="st0">" digits precision = "</span> <span class="sy1">&lt;&lt;</span> γ <span class="sy1">&lt;&lt;</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div></div>
<p>Possible output:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="text source-text"><pre class="de1">The answer is 42
γ as 10⁶ sums of ±ζ(m)/m   = 0.577215
γ as egamma_v&lt;float&gt;       = 0.5772157
γ as egamma_v&lt;double&gt;      = 0.5772156649015329
γ as egamma_v&lt;long double&gt; = 0.5772156649015328606
γ with 34 digits precision = 0.577215664901532860606512090082402</pre></div></div> 
</div>
<h3><span class="mw-headline" id="See_also">See also</span></h3>
<table class="t-dsc-begin">

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="ratio/ratio.html" title="cpp/numeric/ratio/ratio"> <span class="t-lines"><span>ratio</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div>
</td>
<td>   represents exact rational fraction  <br> <span class="t-mark">(class template)</span> </td></tr>
</table>

<!-- 
NewPP limit report
Preprocessor visited node count: 5604/1000000
Preprocessor generated node count: 8333/1000000
Post‐expand include size: 151076/2097152 bytes
Template argument size: 45198/2097152 bytes
Highest expansion depth: 20/40
Expensive parser function count: 0/100
-->

<!-- Saved in parser cache with key mwiki1-mwiki_en_:pcache:idhash:18592-0!*!0!!en!*!* and timestamp 20220723203033 -->
</div>                    <!-- /bodycontent -->
                                        <!-- printfooter -->
                    <div class="printfooter">
                    Retrieved from "<a href="https://en.cppreference.com/mwiki/index.php?title=cpp/numeric/constants&amp;oldid=141025">https://en.cppreference.com/mwiki/index.php?title=cpp/numeric/constants&amp;oldid=141025</a>"                    </div>
                    <!-- /printfooter -->
                                                            <!-- catlinks -->
                    <!-- /catlinks -->
                                                            <div class="visualClear"></div>
                    <!-- debughtml -->
                                        <!-- /debughtml -->
                </div>
                <!-- /bodyContent -->
            </div>
        </div>
        <!-- /content -->
        <!-- footer -->
        <div id="cpp-footer-base" class="noprint">
            <div id="footer">
                        <div id="cpp-navigation">
            <h5>Navigation</h5>
            <ul><li><a href="https://en.cppreference.com/w/cpp/numeric/constants">Online version</a></li><li>Offline version retrieved 2022-07-30 14:05.</li></ul></div>
                        <ul id="footer-info">
                                    <li id="footer-info-lastmod"> This page was last modified on 12 July 2022, at 17:00.</li>
                                    <li id="footer-info-viewcount">This page has been accessed 91,043 times.</li>
                            </ul>
                    </div>
        </div>
        <!-- /footer -->
        <script>if(window.mw){
mw.loader.state({"site":"loading","user":"missing","user.groups":"ready"});
}</script>
<script src="../../../common/skin_scripts.js"></script>
<script>if(window.mw){
mw.loader.load(["mediawiki.action.view.postEdit","mediawiki.user","mediawiki.page.ready","mediawiki.searchSuggest","mediawiki.hidpi","ext.gadget.ColiruCompiler","ext.gadget.MathJax"], null, true);
}</script>
<script src="../../../common/site_scripts.js"></script>
<script type="text/javascript">
var _gaq = _gaq || [];
_gaq.push(['_setAccount', 'UA-2828341-1']);
_gaq.push(['_setDomainName', 'cppreference.com']);
_gaq.push(['_trackPageview']);
</script><!-- Served in 2.345 secs. -->
	</body>
<!-- Cached 20220723203033 -->
</html>